1. Technical Field
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device that prevents optical sheets from being wrinkled.
2. Discussion of the Related Art
Generally, an LCD device includes an LCD module, a driving circuit for driving the LCD module, and a case.
The LCD module includes an LCD panel and a back light unit, wherein the LCD panel includes liquid crystal cells and switching devices, and the back light unit irradiates light to the LCD panel. The liquid crystal cells are arranged in a matrix arrangement and inject a liquid crystal between two glass substrates bonded to each other with a certain gap, and the switching devices respectively switch signals supplied to the liquid crystal cells.
Furthermore, the LCD module includes optical sheets arranged to vertically raise light forwarded from the back light unit to the LCD panel.
The LCD panel, the back light unit and the optical sheets should be fixed to one another in a single body to avoid light loss and also should be protected from damage caused by external impact.
To this end, a case top for LCD device has been provided to encircle the back light unit and the optical sheets including the edge of the LCD panel.
As described above, since the LCD module includes the glass substrates, it is likely that the LCD module may be damaged by external impact. To prevent the LCD module from being damaged by external impact, the case top has been used to protect the outside of the LCD module.
FIG. 1 is an exploded perspective view illustrating a general LCD device.
As shown in FIG. 1, the general LCD device includes an LCD panel 30 displaying images, a fluorescent lamp 31 generating light, a lamp housing 32 encircling the fluorescent lamp 31 in a U shape, a diffusion plate 38, a first prism sheet 37, a second prism sheet 36, a protective sheet 35, a light guide plate 33, and a reflection plate 34. The diffusion sheet, the first prism sheet 37, the second prism sheet 36, the protective sheet 35, the light guide plate 33, and the reflection sheet 34 are sequentially fixed to one surface of the LCD panel 30.
The LCD device further includes a support main 39 receiving and fixing the LCD panel 30 and the back light unit.
The fluorescent lamp 31, the lamp housing 32, the diffusion plate 38, the first prism sheet 37, the second prism sheet 36, the protective sheet 35, the light guide plate 33, and the reflection sheet 34 are referred to as the back light unit.
Meanwhile, the back light unit serves to irradiate light to a display area A of the LCD panel 30. Although not shown, the display area A of the LCD panel includes two transparent substrates provided with polarizers on outer surfaces, and a liquid crystal injected between inner surfaces of the two transparent substrates.
The LCD device further includes a driving circuit 40 driving the display area.
The operation of the back light unit will be described below. If the fluorescent lamp 31 provided on one end of the light guide plate 33 is turned on, light generated from the fluorescent lamp 31 is reflected by the lamp housing 32, and the reflected light is transferred to the end of the light guide plate having no fluorescent lamp through the end of the light guide plate. The light is scattered over the whole surface of the light guide plate 33, and the light is irradiated to the display area of the LCD panel through the diffusion plate 38.
In the LCD device, a thin film transistor formed in the LCD panel controls pixels in accordance with a signal of the driving circuit to selectively pass through the light irradiated to the display area. Images are displayed in the display area of the LCD panel by the pixels which have selectively passed through the light.
Hereinafter, a related art LCD device will be described with reference to the accompanying drawings.
FIG. 2 is a plane view illustrating the related art LCD device and FIG. 3 is an exploded sectional view illustrating the LCD device, taken along line II˜II′ of FIG. 2.
As shown in FIGS. 2 and 3, the related art LCD device includes a support main 2, a back light unit, an LCD panel 10, a cover bottom 14 encircling the bottom and a side of the support main 2, and a case top 16 formed to encircle the edge of the LCD panel 10 and the cover bottom 14. The back light unit and the LCD panel are stacked inside the support main 2.
The support main 2 is a mold and its sidewall is formed by a stair shaped edge surface. The back light unit is provided at the lowest layer inside the support main 2, and the LCD panel 10 is provided on the back light unit.
Also, the LCD panel 10 includes a lower substrate 10b packaged with switching devices (TFTs), and an upper substrate 10a provided with a color filter. A liquid crystal is injected between the lower substrate 10b and the upper substrate 10a. Lower and upper polarizers 22 and 24 are provided below and above the LCD panel 10.
The lower polarizer 22 provided below the LCD panel 10 polarizes light beams supplied from the back light unit and supplies the polarized light beams to the LCD panel 10. The upper polarizer 25 provided above the LCD panel 10 polarizes light beams supplied from the LCD panel 10 and emits the polarized light beams to the outside.
Furthermore, the cover bottom 10 is provided to encircle the bottom and the side of the support main 2. The case top 16 is provided to encircle the top and the side of the support main 2 to fix the support main 2 and the LCD panel 10 to each other.
The back light unit includes a lamp housing 18 provided with a light source 20, a light guide plate 6 converting light emitted from the light source 20 into surface light, optical sheets 12 fixed onto the light guide plate 6 to improve efficiency of the light emitted to the LCD panel 10, and a reflection plate 4 fixed to a rear surface of the light guide plate 6 to reflect the light emitted to the rear surface of the light guide plate 6 toward the LCD panel 10.
Furthermore, the light source 20 corresponds to a power source supplied from an outer power generator and supplies predetermined light to the light guide plate 6. At this time, light beams emitted from the light source 20 to the opposite side of the light guide plate 6 are reflected by the lamp housing 18 and enter the light guide plate 6.
In this case, the light guide plate 6 uniformly distributes the light emitted from the light source 20 over its whole area. In other words, the light guide plate 6 allows uniform light to enter the LCD panel 10 by uniformly distributing the light emitted from the light source 20.
Furthermore, the reflection plate 4 reflects the light emitted to the lower side of the light guide plate. In other words, the reflection plate 4 reflects the light emitted from the light guide plate 6 and thus allows the light to be supplied to the LCD panel 10.
The optical sheets 12 include upper/lower diffusion sheets and upper/lower prism sheets. The optical sheets 12 scatter the light emitted from the light guide plate 6 to allow the light to be uniformly distributed over the surface of the light guide plate. Also, the optical sheets 12 refract and condense the scattered light to increase surface luminance and diffuse the light, thereby obtaining a wide viewing angle.
The support main 2 partially overlaps side portions of the optical sheets 12 to fix the optical sheets 12.
In the aforementioned related art LCD device, the support main 2 has a rectangular shape so that the back light unit including the optical sheets 12 can be inserted thereto.
The light guide plate 6 provided in the support main 2 supplies the light supplied to a light incident portion 30 to the LCD panel 10, so that predetermined images are displayed on the LCD panel 10.
A recent trend of the LCD device is toward a thin and lightweight size. Particularly, the LCD device packaged in a notebook computer essentially requires a thin and lightweight size to allow a user to easily carry it.
However, the support main sagged due to a hook fitting structure with the cover bottom interferes with the optical sheets 12. For this reason, the optical sheets are wrinkled under a high temperature.
A gap between the optical sheets 12 and the support main 2, but if the gap has a too large size, a defect such as wrinkle occurs, which causes another side effect.
Furthermore, the support main supporting the panel in an area excluding an active area corresponding to an image display area is susceptible to bending in view of its structure. Such bending of the support main occurs more seriously in four corners.